Dental composition based on silicone crosslinkable by cation process

ABSTRACT

The invention concerns dental compositions. Said composition comprises (1) a silicone crosslinkable and/or polymerizable by cation process; (2) an efficient amount of at least an initiator such as onium borate; (3) at least a photosensitizer ; and (4) a dental filler present in the composition in a proportion of at least 10 wt. % relative to the composition total weight. Said dental compositions are useful for making dental prostheses or for dental restoration.

The field of the invention is that of dental compositions. Moreprecisely, the dental compositions used in the context of the presentinvention can be used for producing dental prostheses and for dentalrestoration.

Up until now, to produce dental compositions for the preparation ofdental prostheses or of dental restoration materials, it is possible touse resins based on photopolymerizable acrylates. Theseready-to-formulate products exhibit however upon use problems ofirritation and potential problems of toxicity.

In addition, these products have the major disadvantage of causing highvolume shrinkage during their polymerization, which makes their usecomplex and difficult for the production of dental prostheses or ofdental restoration materials. Problems of attachment due to the volumeshrinkage or to the lack of adherence of the polymers used are inparticular observed.

The object of the present invention is to provide novel dentalcompositions which do not exhibit the disadvantages of the prior art.These novel dental compositions, which are polymerizable and/orcrosslinkable in an oral environment, have markedly improved qualities,in particular as regards the very marked reduction in the phenomenon ofshrinkage of the dental compositions used for the production of dentalprostheses or of dental restoration materials.

The polymerizable and/or crosslinkable dental composition according tothe invention comprises:

-   -   (1) at least one crosslinkable and/or polymerizable silicone        oligomer or polymer which is liquid at room temperature or which        is heat-meltable at a temperature of less than 100° C., and        which comprises:        -   at least one unit of formula (FS):            Z—Si            R⁰            _(a)O_((3−a)/2)        -   in which:            -   a=0, 1 or 2,            -   R⁰, identical or different, represents        -   an alkyl, cycloalkyl, aryl, vinyl, hydrogeno or alkoxy            radical, preferably a C₁-C₆ lower alkyl,            -   Z, identical or different, is an organic substituent                comprising at least one reactive epoxy, and/or alkenyl                ether and/or oxetane and/or dioxolane and/or carbonate                functional group, and        -   preferably Z being an organic substituent comprising at            least one reactive epoxy and/or dioxolane functional group,            -   and at least two silicon atoms,    -   (2) an effective quantity of at least one borate-type        photoinitiator,    -   (3) at least one aromatic hydrocarbon photosensitizer with one        or more aromatic nuclei which are substituted or not, having a        residual light absorption of between 200 and 500 nm,    -   (4) and at least one dental filler present in a proportion of at        least 10% by weight relative to the total weight of the        composition.

According to a first advantageous variant of the present invention, thedental composition is polymerizable and/or crosslinkable underactivation by the thermal route and/or by the photochemical route.

In general, the photochemical activation is carried out under UVradiation. More particularly, UV radiation having a wavelength of theorder of 200 to 500 nm is used for the production of dental prosthesesand UV-visible radiation having a wavelength greater than 400 nm for theproduction of restoration materials. A wavelength greater than 400 nmallows crosslinking and/or polymerization in an oral environment.

The silicone polymer or oligomer (1) has the advantage, compared withorganic resins which are crosslinked by the cationic route, of beingtransparent to UV-visible light and therefore its use makes it possibleto obtain materials which are very thick and whose photocrosslinkingoccurs in a short time.

The reactive functional groups Z of the silicone polymer or oligomer (1)may be highly varied. However, particularly advantageous dentalcompositions are obtained when the silicone oligomer or polymer (1)comprises at least one (FS) unit in which Z represents an organicsubstituent Z1 comprising at least one reactive epoxy, and/or dioxolanefunctional group, and preferably at least one reactive epoxy functionalgroup.

According to two advantageous alternatives of the present invention, thesilicone oligomer or polymer (1) with at least one reactive epoxy and/ordioxolane functional group Z1, and preferably at least one reactiveepoxy functional group may:

-   -   (i) either comprise only this (these) type(s) of reactive        functional group(s) Z1,    -   (ii) or comprise other reactive functional groups Z such as the        reactive alkenyl ether, oxetane and/or carbonate functional        groups Z2.

In the case of the first alternative (i), the dental composition mayalso comprise other silicone oligomers and/or polymers comprising otherreactive functional groups Z2 such as alkenyl ether, oxetane and/orcarbonate functional groups and optionally reactive functional groupsZ1.

By way of examples of reactive functional groups Z, these may inparticular be chosen from the following radicals:

-   -   with R″ representing a linear or branched C₁-C₆ alkyl radical.

According to a second advantageous variant of the present invention, thesilicone polymer or oligomer consists of at least one silicone havingthe following average formula:

The cationic photoinitiators are chosen from onium borates (taken ontheir own or as a mixture with each other) of an element of groups 15 to17 of the Periodic Table [Chem. & Eng. News, vol. 63, No. 5, 26 of 4Feb. 1985] or of an organometallic complex of an element of groups 4 to10 of the Periodic Table [same reference].

The cationic entity of the borate is selected from:

-   -   (1) the onium salts of formula (I)        [(R¹)_(n)—A—(R²)_(m)]⁺  (I)    -   in which formula:        -   A represents an element of groups 15 to 17 such as for            example: I, S, Se, P or N,        -   R¹ represents a carbocyclic or heterocyclic C₆-C₂₀ aryl            radical, it being possible for said heterocyclic radical to            contain, as heteroelements, nitrogen or sulfur,        -   R² represents R¹ or a linear or branched C₁-C₃₀ alkyl or            alkenyl radical; said radicals R¹ and R² being optionally            substituted with a C₁-C₂₅ alkoxy, C₁-C₂₅ alkyl, nitro,            chloro, bromo, cyano, carboxyl, ester or mercapto group,        -   n is an integer ranging from 1 to v+1, v being the valency            of the element A,        -   m is an integer ranging from 0 to v−1 with n+m=v+1,    -   (2) the oxoisothiochromanium salts described in patent        application WO 90/11303, in particular the sulfonium salt of        2-ethyl-4-oxoisothiochromanium or        2-dodecyl-4-oxoisothiochromanium,    -   (3) the sulfonium salts in which the cationic entity comprises:        -   3₁ at least one polysulfonium entity of formula (II.1):            in which:    -   the symbols Ar¹, which are identical or different, each        represent a monovalent phenyl or naphthyl radical, optionally        substituted with one or more radicals chosen from: a linear or        branched C₁-C₁₂, preferably C₁-C₆, alkyl radical, a linear or        branched C₁-C₁₂, preferably C_(-C) ₆, alkoxy radical, a halogen        atom, an —OH group, a —COOH group, an ester group —COO-alkyl        where the alkyl portion is a linear or branched C₁-C₁₂,        preferably C₁-C₆, residue, and a group of formula —Y⁴—Ar² where        the symbols Y⁴ and Ar² have the meanings given just below, —the        symbols Ar², which are identical or different, each represent a        monovalent phenyl or naphthyl radical, optionally substituted        with one or more radicals chosen from: a linear or branched        C₁-C₁₂, preferably C₁-C₆, alkyl radical, a linear or branched        C₁-C₁₂, preferably C₁-C₆, alkoxy radical, a halogen atom, an —OH        group, a —COOH group, an ester group —COO-alkyl where the alkyl        portion is a linear or branched C₁-C₁₂, preferably C₁-C₆,        residue,    -   the symbols Ar³, which are identical or different, each        represent a divalent phenylene or naphthylene radical,        optionally substituted with one or more radicals chosen from: a        linear or branched C₁-C₁₂, preferably C₁-C₆, alkyl radical, a        linear or branched C₁-C₁₂, preferably C₁-C₆, alkoxy radical, a        halogen atom, an —OH group, a —COOH group, an ester group        —COO-alkyl where the alkyl portion is a linear or branched        C₁-C₁₂, preferably C₁-C₆, residue,    -   t is an integer equal to 0 or 1, with the additional conditions        according to which:        -   + when t=0, the symbol Y is then a monovalent radical Y¹            representing the group of formula:            where the symbols Ar¹ and Ar² possess the meanings given            above,

-   + when t=1:    -   on the one hand, the symbol Y is then a divalent radical having        the following meanings Y² to Y⁴:    -   Y²: a group of formula:        where the symbol Ar² has the meanings given above,    -   Y³: a single valency bond,    -   Y⁴: a divalent residue chosen from:        a linear or branched C₁-C₁₂, preferably C₁-C₆, alkylene residue        and a residue of formula —Si (CH₃)₂O—,    -   on the other hand, in the case solely where the symbol Y        represents Y³ or Y⁴, the (terminal) radicals Ar¹ and Ar²        possess, in addition to the meanings given above, the        possibility of being linked to each other by the residue Y′        consisting of Y′¹ a single valency bond or of Y′² a divalent        residue chosen from the residues cited in relation to the        definition of Y⁴, which is inserted between the carbon atoms,        opposite each other, situated on each aromatic ring at the ortho        position with respect to the carbon atom directly linked to the        cation S⁺;    -   3₂ and/or at least one monosulfonium entity possessing single        cationic center S⁺ per mol of cation and consisting, in most        cases, of entity of formula (II.2):        in which Ar¹ and Ar² have the meanings given above in relation        to formula (III.1), including the possibility of directly        linking to each other only one of the radicals Ar¹ to Ar² in the        manner indicated above in relation to the definition of the        additional condition in force when t=1 in formula (II), calling        into play the residue Y′;    -   (4) the organometallic salts of formula (III):        (L¹L²L³M)^(+q)        in which formula:    -   M represents a group 4 to 10 metal, in particular iron,        manganese, chromium or cobalt,    -   L¹ represents 1 ligand bound to the metal M by π electrons,        which ligand is chosen from the ligands η³-alkyl,        η⁵-cyclopendadienyl and η⁷-cycloheptratrienyl and the        η⁶-aromatic compounds chosen from the optionally substituted        η⁶-benzene ligands and the compounds having from 2 to 4        condensed rings, each ring being capable of contributing to the        valency layer of the metal M by 3 to 8 π electrons;    -   L² represents a ligand bound to the metal M by π electrons,        which ligand is chosen from the ligands η⁷-cycloheptratrienyl        and the η⁶-aromatic compounds chosen from the optionally        substituted ligands η6 -benzene and the compounds having from 2        to 4 condensed rings, each ring being capable of contributing to        the valency layer of the metal M by 6 or 7 π electrons;    -   L³ represents from 0 to 3 ligands, which are identical or        different, linked to the metal M by σ electrons, which ligand(s)        is (are) chosen from CO and NO₂ ⁺; the total electron charge q        of the complex to which L¹, L² and L³ contribute and the ionic        charge of the metal M being positive and equal to 1 or 2;

The anionic borate entity has the formula [BX_(a)R_(b)]⁻ in which:

-   -   a and b are integers ranging, for a, from 0 to 3 and, for b,        from 1 to 4 with a+b=4,    -   the symbols x represent:        -   a halogen atom (chlorine, fluorine) with a=0 to 3,        -   an OH functional group with a=0 to 2,    -   the symbols R are identical or different and present:        -   -   a phenyl radical substituted with at least one                electron-attracting group such as for example CF₃, CF₃,                NO₂, CN, and/or with at least 2 halogen atoms (fluorine                most particularly), this being when the cationic entity                is an onium of an element of groups 15 to 17,            -   a phenyl radical substituted with at least one element                or one electron-attracting group, in particular a                halogen atom (fluorine most particularly), CF₃, OCF₃,                NO₂, CN, this being when the cationic entity is an                organometallic complex of an element of groups 4 to 10,            -   an aryl radical containing at least two aromatic nuclei                such as for example biphenyl, naphthyl, optionally                substituted with at least one electron-attracting group                or element, in particular a halogen atom (fluorine most                particularly), OCF₃, CF₃, NO₂, CN, regardless of the                cationic entity.

Without being limiting, more details are given below as regards thesubclasses of onium borate and of borate of organometallic salts moreparticularly preferred in the context of the use in accordance with theinvention.

According to a first preferred variant of the invention, the entity ofthe anionic borate entity which are most particularly suitable are thefollowing:

-   1′: [B(C₆F₅)₄]⁻ 5′: [B(C₆H₃(CF₃)₂)₄]⁻-   2′: [(C₆F₅)₂BF₂]⁻ 6′: [B (C₆H₃F₂)₄]⁻-   3′: [B(C₆H₄CF₃)₄]⁻ 7′: [C₆F₅BF₃]⁻-   4′: [B(C₆F₄OCF₃)₄]⁻

According to a second preferred variant of he invention, the onium salts(1) which can be used re described in numerous documents, in particularin patents U.S. Pat. Nos. 4,026,705, 4,032,673, 4,069,056, 4,136,102,4,173,476. Among these, the following cations will be most particularlypreferred:

-   [(Φ)₂I]⁺ [C₈H₁₇—O—Φ—I—Φ]⁻ [(Φ)—CH₃)₂I]⁺-   [C₁₂H₂₅—Φ—I—Φ]⁺ [C₈H₁₇—O—Φ)₂I]⁻⁰[(C₈H₁₇—O—Φ—I—Φ)]⁺-   [(Φ)₃S]⁺ [(Φ)₂—S—Φ—O—C₈H₁₇]⁺ [(CH₃—Φ—I—Φ—CH(CH₃)₂]⁺-   [Φ—S—Φ—S—(Φ)₂]⁺ [(C₁₂H₂₅—Φ)₂I]⁺ [(CH₃—Φ—I—Φ—OC₂H₅]⁺

According to a third preferred variant, the organometallic salts (4)which can be used are described in the documents U.S. Pat. Nos.4,973,722, 4,992,572, EP-A-203 829, EP-A-323 584 and EP-A-354 181. Theorganometallic salts most readily selected according to the inventionare in particular:

-   -   (η⁵-cyclopentadienyl) (η⁶ -toluene) Fe⁺,    -   (η⁵-cyclopentadienyl) (η⁶-methyl-1-naphthalene) Fe⁺,    -   (η⁵-cyclopentadienyl) (η⁶-cumene) Fe⁺,    -   bis(η⁶-mesitylene) Fe⁺,    -   bis (η⁶-benzene) Cr⁺.

In agreement with these three preferred variants, the following productsmay be mentioned by way of examples of photoinitiators of the oniumborate type:

-   [(Φ)₂I]⁺, [B(C₆F₅)₄]⁻ [(C₈H₁₇)—O—Φ—I—Φ)]⁺, [B(C₆F₅ ₄]⁻-   [C₁₂H₂₅—ΦI—Φ]⁺, [B(C₆F₅)₄]⁻ [(C₈H₁₇—O—Φ)₂I]⁺, [B(C₆F₅)₄]⁻-   [(C₈H₁₇)—O—Φ—I—Φ)]⁺, [B(C₆F₅)₄]⁻ [(Φ)₃S]⁺, [B(C₆F₅)₄]⁻-   [(Φ)₂S—Φ—O—C₈H₁₇]⁺, [B(C₆H₄CF₃)₄]⁻[(C₁₂H₂₅—Φ)₂I]⁺, [B(C₆F₅)₄]⁻-   [(Φ)₃S]⁺, [B(C₆F₄OCF₃)₄]⁻ [(Φ—CH₃)₂I]⁺, [B(C₆F₅)₄]⁻-   [(Φ—CH₃)₂I]⁺, [B(C₆F₄OCF₃)₄]⁻ [CH₃—Φ—I—Φ—CH (CH₃)₂]⁺, [B(C₆F₅)₄]⁻    -   (η⁵-cyclopentadienyl) (η6-toluene) Fe⁺, [B(C₆F₅)₄]⁻    -   (η⁵-cyclopentadienyl) (η⁶-methyl-1-naphthalene) Fe⁺, [B(C₆F₅)₄]⁻    -   (η⁵-cyclopentadienyl) (η⁶-cumene) Fe⁺, [B(C₆F₅)₄]⁻

As another literary reference for defining the onium borates (1) and (2)and the borates of organometallic salts (4), there may be mentioned theentire content of patent applications EP 0 562 897 and 0 562 922. Thiscontent is integrally incorporated by reference into the presentdisclosure.

As another example of onium salt which can be used as photoinitiator,there may be mentioned those disclosed in American patents U.S. Pat.Nos. 4,138,255 and 4,310,469.

Other cationic photoinitiators may also be ed, e.g.:

-   -   those marketed by Union-Carbide (photoinitiator 6990 and 6974        triarylsulfonium hexafluorophosphate and hexafluoroantimonate),    -   the salts of iodonium hexafluorophosphate or        hexafluoroantimonate,    -   or the ferrocenium salts of these various anions.

The nature of the photosensitizer contained in the dental compositionaccording to the invention may be highly varied. In the context of theinvention, it corresponds in particular to one of the following formulae(IV) to (XXII):

formula (IV)

-   -   in which:    -   when n=1, Ar¹ represents an aryl radical containing from 6 to 18        carbon atoms, a tetrahydronaphthyl, thienyl, pyridyl or furyl        radical or a phenyl radical carrying one or more substituents        chosen from the group consisting of F, Cl, Br, CN, OH, linear or        branched C₁-C₁₂ alkyls, —CF³, —OR⁶, —OPhenyl, —SR⁶, —SPhenyl,        —SO₂Phenyl, —COOR⁶, —O—(CH₂—CH═CH₂), —O (CH₂H₄—O)_(m)—H,        —O(C₃H₆O)_(m)—H, m being between 1 and 100,    -   when n=2, Ar₁ represents a C₆-C₁₂ arylene radical or a        phenylene-T-phenylene radical where T represents —O—, —S—, —SO₂—        or —CH₂—,    -   X represents a group —OR⁷ or —OSiR⁸ (R⁹)₂ or forms, with R⁴, a        group —O—CH (R¹⁰)—,    -   R₄ represents a linear or branched C₁-C₈ alkyl radical which is        unsubstituted or which carries an —OH, —OR⁶, C₂-C₈ acyloxy, —CF³        or —CN group, a C₃ or C₄ alkenyl radical, a C₆ to C₁₈ aryl        radical, a C₇ to C₉ phenylalkyl radical,    -   R⁵ has one of the meanings given for R⁴ or represents a radical        —CH₂CH₂R¹¹ , or alternatively forms with R⁴ a C₂-C₈ alkylene        radical or a C₃-C₉ oxa-alkylene or aza-alkylene radical,    -   R⁶ represents a lower alkyl radical containing from 1 to 12        carbon atoms,    -   R⁷ represents a hydrogen atom, a C₁-C₁₂ alkyl radical, a C₂-C₆        alkyl radical carrying an —OH, —OR⁶ or —CN group, a C₃-C₆        alkenyl radical, a cyclohexyl or benzyl radical, a phenyl        radical optionally substituted with a chlorine atom or a linear        or branched C₁-C₁₂ alkyl radical, or a 2-tetrahydropyranyl        radical,    -   R⁸ and R⁹ are identical or different and each represent a C₁-C₄        alkyl radical or a phenyl radical,    -   R¹⁰ represents a hydrogen atom, a C₁-C₈ alkyl radical or a        phenyl radical,    -   R¹¹ represents a radical —CONH₂, —CONHR⁶, —CON(R⁶)₂, —P(O)        (OR⁶)₂ or 2-pyridyl;

Formula (V)

-   -   in which:    -   Ar² has the same meaning as Ar¹ of formula (IV) in the case        where n=1,    -   R¹⁵ represents a radical chosen from the group consisting of a        radical Ar², a linear or branched C₁-C₁₂ alkyl radical, a C₆-C₁₂        cycloalkyl radical, and a cycloalkyl radical forming a C₆-C₁₂        ring with the carbon of the ketone or a carbon of the radical        Ar², it being possible for these radicals to be substituted with        one or more substituents chosen from the group consisting of —F,        —Cl, —Br, —CN, —OH, —CF₃, —OR⁶, —SR⁶, —COOR⁶, the linear or        branched C₁-C₁₂ alkyl radicals optionally carrying an —OH, —OR⁶        and/or —CN group, and the linear or branched C₁-C₈ alkenyl        radicals;

Formula (VI)

-   -   in which:    -   Ar³ has the same meaning as Ar¹ of formula (IV) in the case        where n=1,    -   R¹⁶, identical or different, represents a radical chosen from        the group consisting of a radical Ar³, a radical —(C═O)—Ar³, a        linear or branched C₁-C₁₂ alkyl radical, a C₆-C₁₂ cycloalkyl        radical, it being possible for these radicals to be substituted        with one or more substituents chosen from the group consisting        of —F, —Cl, —Br, —CN, —OH, —CF₃, —OR⁶, —SR⁶, —COOR⁶, the linear        or branched C₁-C₁₂ alkyl radicals optionally carrying an —OH,        —OR⁶ and/or —CN group, and the linear or branched C₁-C₈ alkenyl        radicals;

Formula (VII)

-   -   in which:    -   R⁵, which are identical or different, have the same meanings as        in formula (III),    -   Y, which are identical or different, represent X and/or R⁴,    -   Z represents:    -   a direct bond,    -   a C₁-C₆ divalent alkylene radical, or a phenylene, diphenylene        or phenylene-T-phenylene radical, or alternatively forms, with        the two substituents R⁵ and the two carbon atoms carrying these        substituents, a cyclopentane or cyclohexane nucleus,    -   a divalent group —O—R¹²—O—, —O—SiR⁸R⁹—O—SiR⁸R⁹—O—, or        —O—SiR⁸R⁹—O—,    -   R¹² represents a C₂-C₈ alkylene, C₄-C₆ alkenylene or xylylene        radical, and Ar⁴ has the same meaning as Ar¹ of formula (IV) in        the case where n=1.

Family of Thioxanthones of Formula (VIII):

-   -   R¹⁷, identical or different substituent(s) on the aromatic        nucleus (nuclei), represent a linear or branched C₁-C₁₂ alkyl        radical, a C₆-C₁₂ cycloalkyl radical, a radical Ar¹, a halogen        atom, an —OH, —CN, —NO₂, —COOR , —CHO, Ophenyl, —CF₃, —SR⁶,        —Sphenyl, —SO₂phenyl, Oalkenyl, or —SiR⁶ ₃ group.

Family of Xanthenes of Formula (IX):

Family of Xanthones of Formula (X):

Family of the Naphthalene of Formula (XI):

Family of the Anthracene of Formula (XII):

Family of the Phenanthrene of Formula (XIII):

Family of the Pyrene of Formula (XIV):

Family of the Fluorene of Formula (XV):

Family of the Fluoranthene of Formula (XVI):

Family of the Chrysene of Formula (XVII):

Family of the Fluorene of Formula (XVIII):

-   -   with x+0 to 8, for example 2,7-dinitro-9-fluorenone,

Family of the Chromone of Formula (XIX):

Family of the Eosin of Formula (XX):

Family of the Erythrosin of Formula (XXI):

Family of the Biscoumarins of Formula (XXII):

-   -   R¹⁸, identical or different, has the same meaning as R¹⁷ or        represents a group —NR⁶ ₂, for example        3,3′-carbonylbis(7-diethylaminocoumarin) and 3,3′-carbonyl        -bis(7-methoxycoumarin).

Other sensitizers can be used. In particular, the photosensitizersdescribed in the documents U.S. Pat. Nos. 4,939,069; 4,278,751;4,147,552 may be used.

In the context of the present invention, the photosensitizers have aresidual absorption of UV light between 200 and 500 nm, preferably 400to 500 nm for the preparations of dental prostheses. For dentalrestoration, a photosensitizer having a residual absorption of UV lightabove 400 nm will be preferred.

According to a preferred variant, the photosensitizers will be chosenfrom those of the families (IV), (VII) and (VIII). By way of examples,the following photosensitizers will be mentioned: 4,4′-dimethoxybenzoin;2-4-diethylthioxanthone 2-ethylanthraquinone; 2-methylanthraquinone;1,8-dihydroxyanthraquinone; dibenzoylperoxide;2,2-dimethoxy-2-phenylaceto- benzoin; phenone; 2-hydroxy-2-methylpropio-benzaldehyde; phenone; 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)- ketone;

2-isopropylthioxanthone; 1-chloro-4-propoxy- thioxanthone;4-isopropylthioxanthone; and the mixture thereof.

Various types of fillers can be used for preparing the compositionsaccording to the invention. The fillers are chosen according to thefinal use of the dental composition: these affect important propertiessuch as appearance, penetration of UV radiation, as well as themechanical and physical properties of the material obtained aftercrosslinking and/or polymerization of the dental composition.

As reinforcing filler, there may be used treated or untreated pyrogenicsilica fillers, amorphous silica fillers, quartz, glass or nonglassyfillers based on oxides of zirconium, barium, calcium, fluorine,aluminum, titanium, zinc, borosilicates, aluminosilicates, talc,spherosil, yterbium trifluoride, fillers based on polymers in groundpowder form, such as inert or functionalized methyl polymethacrylates,polyepoxides or polycarbonates.

By way of example, there may be mentioned:

-   -   inert fillers based on methyl polymethacrylate LUXASELF from the        company UGL, which can be used in the dental field which are        pigmented in pink,    -   hexamethyldisilazane-treated fumed silica fillers having a        specific surface area of 200 m²/g,    -   untreated fumed silica fillers (“aerosil” AE200 marketed by        DEGUSSA).

According to an advantageous variant of the invention, the fillers andin particular the silica fillers are treated before use at 120° C. witha quantity of less than 10% w/w of silicone comprising at least one unitof formula (XXIII):Z—Si

R⁰

_(a)O_((3−a)/2)

-   -   such that Z′ has the same definition as Z−a=0,1,2 or 3    -   with at least one silicon atom.

There may be. mentioned by way of example the polymer described belowwith Z=epoxide and Z=trialkoxysilyl

In this case for the treatment of silicone-containing filler(s), inparticular silica, with. this type of polymer, the material obtainedafter crosslinking has a mechanical strength, a modulus of elasticityand a resistance to compression which are markedly improved.

In addition to the reinforcing fillers, pigments may be used to colorthe dental composition according to the invention envisaged and theethnic groups.

For example, red pigments are used in the presence of microfibers forthe dental compositions used for the preparation of dental prostheses inorder to simulate the blood vessels.

Pigments based on metal oxides (iron and/or titanium and/or aluminumand/or zirconium oxides, and the like) are also used for the dentalcompositions used for the preparation of restoration material, in orderto obtain a crosslinked material having an ivory color.

Other additives may be incorporated into the dental compositionsaccording to the invention. For example, biocides, stabilizers,flavoring agents, plasticizers and adherence promoters.

Among the additives which may be envisaged, there will be advantageouslyused crosslinkable and/or polymerizable coreagents of the organic type.These coreagents are liquid at room temperature or are hot-meltable at atemperature of less than 100° C., and each coreagent comprises at leasttwo reactive functional groups such as oxetane-alkoxy, oxetane-hydroxyl,oxetane-alkoxysilyl, carboxyl-oxetane, oxetane-oxetane, alkenylether-hydroxyl, alkenyl ether-alkoxysilyl, epoxy-alkoxy,epoxy-alkoxysilyls, dioxolane-dioxolane-alcohol, and the like.

The dental compositions according to the invention may be used fornumerous dental applications, and in particular in the field of dentalprostheses, in the field of dental restoration and in the field oftemporary teeth.

The dental composition according to the invention is preferably providedin the form of a single product containing the various components(“monocomponent”) which facilitates its use, in particular in the fieldof dental prostheses. Optionally, the stability of this product may beprovided for by organic derivatives with amine functional groupsaccording to the teaching of the document WO 98/07798.

In the field of dental prostheses, the product in the “monocomponent”form may be deposited with the aid of a syringe directly on the plastermodel or in a core. Next, it is polymerized (polymerization by possiblesuccessive layers) with the aid of a UV lamp (visible light spectrum200-500 nm)

In general, it is possible to produce a lasting and esthetic dentalprosthesis in 10 to 15 min.

It should be noted that the products obtained from the dentalcomposition according to the invention are nonporous. Thus, after anoptional polishing with the aid of a felt brush, for example, thesurface of the dental prostheses obtained is smooth and bright andtherefore does not require the use of varnish.

The applications in the field of dental prostheses are essentially thoseof the joined prosthesis, which can be divided into two types:

-   -   full prosthesis in the case of a patient with absolutely no        teeth    -   partial prosthesis due to the absence of several teeth,        resulting either in a provisional prosthesis, or a skeleton        brace.

In the field of dental restoration, the dental composition according tothe invention may be used as material for filling the anterior andposterior teeth in different colors (for example “VITA” colors), whichis rapid and easy to use.

The dental composition being nontoxic and polymerizable in thick layers,it is not essential to polymerize the material in successive layers. Ingeneral, a single injection of the dental composition is sufficient.

The preparations for dental prostheses and for restoration materials arecarried out according to techniques which are customary in the art.

In the case of application of the dental composition as a tooth, eitherthe tooth may be pretreated with a bonding primer or the dentalcomposition may be prepared as a mixture with a bonding primer beforeits use. However, it is not essential to use a bonding primer in orderto use the dental composition according to the invention.

The following examples and tests are given by way of illustration. Theymake it possible in particular to understand more clearly the inventionand to highlight some of its advantages and to illustrate a few of itsvariant embodiments.

EXAMPLE AND TESTS

The product used in the compositions of the examples are the following:

product (A):

Product (B): this product is a mixture of siloxanes, whose viscosity is23.5 mPa.s and in which the proportions by weight and formulae B₁, B₂and B₃ are given below:

with 89% of B₁ where a=0, 9% of B₁ where a=1; 0.2% of B₁ where a=2;

with 0.3% of B2 where a=0;

and with 1.5% of B3 where a=0 and b=1.

product (P1):

Product (PS1): isopropylthioxanthone marketed under the trademarkQuantacure ITX by the company RAHN.

Example 1

Composition for Dental Prosthesis

The following are mixed using a three-blade stirrer:

-   -   100 parts of siloxane (A) stabilized with 50 ppm of Tinuvin 765;    -   1 part of photoinitiator (P1) at 75% in ethyl acetate;    -   0.028 part of photosensitizer (PS1);    -   150 parts of a pink-pigmented, polymethyl methacrylate-based        inert filler (product LUXASELF from UGL dentaire).

The composition obtained is perfectly stable in the absence of light forseveral months at room temperature. This composition can be workedmanually and for several hours in the presence of daylight.

A test piece 2.8±0.3 mm thick is prepared in a glass dish 64 mm long(model), 10 mm wide (model) and open at the top by pouring the preparedcomposition (“monocomponent”) into the dish.

The composition is dried by passing the dish for 1 to 2 seconds (3m/min) under a UV lamp of 200 W/cm power corresponding to the excitationof a mixture of mercury and gallium and emitting in the UV-visible rangeabove 400 nm.

The product obtained is unmolded by breaking the glass.

The SHORE D hardness of the two polymerized compositions is determinedon each side of the item made immediately after crosslinking. ImmediateMeasurement Example 1 measurement after 10 hours Irradiated surface: 7085 Bottom surface 60 85

The Shore D hardness continues to change substantially over a few hours.

The volume shrinkage is very low and excellent size stability isobtained.

The loss of mass is less than 1%.

The product may be used with or without bonding primer in the presenceof artificial teeth or of natural teeth.

More generally, the properties of the material obtained are in agreementwith the DIN/ISO 1567 standard.

Example 2

Composition for Dental Restoration

A composition for dental restoration is prepared by mixing:

-   -   200 parts of siloxane (A) stabilized with 50 ppm of Tinuvin 765;    -   1.8 parts of photoinitiator (P1) at 75% in ethyl acetate;    -   0.0178 part of photosensitizer (PS1);    -   52 parts of hexamethyldisilazane-treated fumed silica having a        specific surface area of 200 m²/g;    -   20 parts of untreated amorphous silica dried for 4 hours at        200° C. before formulation.

A flowing composition is obtained which has a translucent grayappearance.

The crosslinking-polymerization operation is carried out using a lampemitting a light spot emitted through a curved light tip 8 mm indiameter. The source is an Optibulb 80 W lamp (DEMETRON Optilux 500) forwavelengths of between 400 and 520 nm.

The dental composition is applied in a tooth. A thickness of 5 mm iscrosslinked in less than 30 seconds.

A SHORE D hardness of 50 is obtained immediately and can reach 80 to 100within a few hours.

No loss is observed in size stability. The porosity of the crosslinkedmaterial, based on observation of a section under a microscope, is zero.

The color of the composite after crosslinking is close to ivory color.

Example 3

Composition for Dental Restoration

The same concentrations of components and the same procedure as above inExample 2 are used.

However, the mixture of fillers is treated, before use, at 120° C. with5% w/w of silicone of average general formula containing less than 50ppm of residual platinum:

The restoration material obtained after crosslinking according to theprocedure of Example 2 has a better mechanical strength, an improvedmodulus of elasticity and a better compression resistance.

A SHORE D hardness of 80 is obtained immediately.

The size stability and the porosity properties of the material areexcellent.

Example 4

Dental Precomposition

A dental precomposition, prepared without fillers, is obtained by mixingusing a magnetic stirrer bar:

-   -   1 part of siloxane (A) having a density of 0.997, stabilized        with 50 ppm of Tinuvin 765,    -   0.01 part of photoinitiator (P1) at 10% in solution, dissolved        directly in siloxane A,    -   0.00028 part of photosensitizer (PS1) contained in the        photoinitiator (P1).

The crosslinking operation is carried out in a manner identical to thatof Example 2. A composition 5 mm thick is crosslinked in less than 30seconds.

The density of the crosslinked composition is measured using a brasspycnometer and its value is 1.0274. The volume shrinkage is therefore3.05% [=(1.0274-0.997)/0.997×100] in the absence of fillers.Consequently, a dental composition of this type, formulated with morethan 50% of filler, will have a very low volume shrinkage which is lessthan 1.5%.

Example 5

Dental Precomposition

-   -   (a) A dental precomposition prepared without fillers is obtained        by mixing using a three-blade stirrer,    -   10 parts of siloxane (A) having a density of 0.997, stabilized        with 50 ppm of Tinuvin 765,    -   0.01 part of photoinitiator (P1) dissolved directly in silicone        (A),    -   and 62 ppm of photosensitizer (PS1) contained in the        photoinitiator.

Eight grams of this dental precomposition are then placed in an opencylindrical aluminum cup in a manner such that the volume occupiedrepresents a thickness of about 6 mm.

The liquid is photocrosslinked by passing the cup under a UV lampdelivering, through a pane of glass 6 mm thick, UV-V (>390 nm) 0.6W/cm². The UV-V (>390 nm) dose received is 0.4 J/cm² at 10 m/min.

The degree of conversion of the epoxy functional groups immediatelyafter polymerization is measured from the residual heat of reactionrecorded by differential calorimetry. The residual heat is 17 J/grelative to a noncrosslinked sample which represents 237 J/g. Theeffective degree of conversion of the epoxy functional groups with 0.1%photoinitiator is therefore 93%.

-   -   (b) The same composition as above in (a) is prepared by adding        5% w/w of 3-ethyl-3-(hydroxymethyl)oxetane during the        preparation of the composition. The composition is then        crosslinked in the same manner as above in (a).

The degree of conversion of the epoxy functional groups is 99.3% with aresidual heat of 1.5 J/g.

-   -   (c) The same composition as above in (a) is prepared by adding        10% w/w of 3-ethyl-3-(hydroxymethyl)oxetane during the        preparation of the composition. The composition is then        crosslinked in the same manner as above in (a).

The degree of conversion of the epoxy functional groups is 99.95% with aresidual heat of 0.1 J/g.

Example 6

Composition for Dental Prosthesis or Dental Restoration Material

The following are mixed using a three-blade stirrer:

-   -   95 parts of siloxane (A) stabilized with 50 ppm of Tinuvin 765,    -   62 ppm of photosensitizer (PS1),    -   0.5 part of photoinitiator (P1) at 10% in siloxane (A),    -   5 parts of 3-ethyl-3-(hydroxymethyl)-oxetane,    -   and 120 parts of precipitated silica (ground quartz).

A dental composition is obtained with is opaque, gray in color,nonflowing and easy to handle.

The crosslinking operation is carried out in manner identical to that ofExample 2. A composition 5 mm thick crosslinks in less than 30 seconds.

The color of the material after crosslinking is close to ivory color.

The material is suitable in particular for dental prosthesis use, inparticular the stiffness is greater than 80 Mpa according to the ISO1567 standard.

Example 7

Dental Composition

This composition is formulated with:

-   -   95 parts of silicone (B),    -   62 ppm of photosensitizer (PS1),    -   0.5 part of photoinitiator (P1) at 10% in siloxane (B),    -   5 parts of the oxetane 3-ethyl-3-(hydroxymethyl)oxetane,    -   and 120 parts of precipitated silica (ground quartz).

The crosslinking operation is carried out in a manner identical to thatof Example 2.

The stiffness values found are greater than 80 Mpa according to the ISO1567 standard.

Example 8

Dental Precomposition

A dental precomposition M1 prepared without fillers is obtained bymixing using a three-blade stirrer:

-   -   100 parts of a silicone composition (B) having a density of        0.997 and stabilized with 50 ppm of Tinuvin 765,    -   0.1 part of photoinitiator (P1) at 10% in solution, dissolved        directly in silicone (B),    -   and 0.028 part of photosensitizer (PS1).

A portion of the composition obtained M1 is removed so as to crosslinkit. The crosslinking operation is carried out in a manner identical tothat of Example 2. A composition 5 mm thick crosslinks in less than 30seconds.

The density of the crosslinked material, measured using a brasspycnometer, is 1.0274. The volume shrinkage is therefore 3.05%[=(1.0274-0.997)/0.997×100] in the absence of fillers. Consequently, adental composition of this type, formulated with more than 50% offillers, will have a very low volume shrinkage which is less than 1%.

Example 9

Dental Precomposition

-   -   (a) Eight grams of M1 of Example 8 are placed in an open        cylindrical aluminum cup such that the volume occupied        represents a thickness of about 6 mm.

The photocrosslinking of M1 and the calculation of the degree ofconversion of the epoxy functional groups are carried out according tothe methods described in Example 5.

The residual heat is 17 J/g relative to a noncrosslinked sample whichrepresents 237 J/g. Consequently, the effective degree of conversion ofthe epoxy functional groups with 0.1% of photoinitiator is therefore93%.

-   -   (b) The photocrosslinking and the calculation of the degree of        conversion of the epoxy functional groups are also carried out        for a composition M1 containing 5% w/w of a silicone oil of        formula B₁ with a=12 on average.

The degree of conversion of the epoxy functional groups is 99% with aresidual heat of 1.5 J/g.

-   -   (c) The photocrosslinking and the calculation of the degree of        conversion of the epoxy functional groups are also carried out        for a composition M1 containing 5% w/w of a silicone oil with        a=12 on average and of formula:

The degree of conversion of the epoxy functional groups is 99% with aresidual heat of 5 0.1 J/g.

-   -   (d) The photocrosslinking and the calculation of the degree of        conversion of the epoxy functional groups are also carried out        for a composition M1 containing 5% by weight of siloxane resin        of the MQM^(EPoXY) type containing 0.5% by weight of        hydroxysilyl functional groups and 2% by weight of epoxy        functional group (mass 43).

The degree of conversion of the epoxy functional groups is 99%.

Example 10

Composition for Dental Prosthesis or Dental Restoration Material

The following are mixed using a three-blade stirrer:

-   -   100 parts of silicone (B),    -   62 ppm of photosensitizer (PS1),    -   0.5 part of photoinitiator (P1) at 10% in solution in silicone        (B),    -   and 120 pares of precipitated silica (ground quartz).

A mixture is obtained which is opaque, gray in color, nonflowing andcapable of being handled.

The crosslinking operation is carried out in a manner identical to thatof Example 2. A composition 5 mm thick is crosslinked in less than 30seconds. The color of the material after crosslinking is similar toivory color.

The composition, in this case, is suitable in particular for dentalprostheses, in particular the stiffness is greater than 80 Mpa accordingto the ISO 1567 standard.

Example 11

Dental Composition

The following are mixed using a three-blade stirrer:

-   -   95 parts of silicone (B) stabilized with 50 ppm of Tinuvin 765,    -   62 ppm of photosensitizer (PS1),    -   0.5 part of photoinitiator (P1) at 10% in silicone (B),    -   5 parts of polydimethylsiloxane B1 where a =12 on average,    -   and 120 parts of precipitated silica (ground quartz).

The crosslinking operation is carried out in a manner identical to thatof Example 2. The measured stiffness values are greater than 80 Mpaaccording to the ISO 1567 standard.

1-11. (canceled)
 12. A low shrinking polymerizable or crosslinkabledental composition comprising a mixture of: (1) at least onecrosslinkable and/or polymerizable silicone oligomer or polymer which isliquid at room temperature or which is heat-meltable at a temperature ofless than 100° C., and which comprises: at least one unit of formula(FS):Z—SiR_(a) ⁰—O_((3−a)/2) wherein: a=0, 1 or 2, R⁰, identical ordifferent, represents an alkyl, cycloalkyl, aryl, vinyl, hydrogeno oralkoxy radical, Z, identical or different, is an organic substituentcomprising at least one reactive epoxy, or alkenyl ether or oxetane ordioxolane or carbonate functional group, and at least two silicon atoms,(2) at least one aromatic hydrocarbon photosensitizer, having a residuallight absorption of between 200 and 500 nm, and selected from the groupconsisting of the following formulae (VIII), (X), (XII) and (XXII):thioxanthones of formula (VIII):

wherein: m=0 to 8, R¹⁷, identical or different substituent(s) on thearomatic nucleus (nuclei), represent a linear C₁-C₁₂ alkyl radical, abranched C₁-C₁₂ alkyl radical, a C₆-C₁₂ cycloalkyl radical, a radicalAr¹, a halogen atom, an —OH, —CN, —NO₂, —COOR⁶, —CHO, Ophenyl, —CF₃,—SR⁶, —Sphenyl, —SO₂phenyl, Oalkenyl, or —SiR⁶ ₃ group; xanthones offormula (X):

wherein p=0 to 8 anthracene of formula (XII):

wherein=0 to 10, and biscoumarins of formula (XXII):

wherein: R¹⁸, identical or different, has the same meaning as R¹⁷ aboveor represents a group: —NR⁶ ₂, wherein R₆ represents a linear C₁-C₁₂alkyl radical, (3) at least one dental filler present in a proportion ofat least 10% by weight relative to the total weight of the composition,and (4) an effective quantity of at least one borate-typephotoinitiator, whose cationic entity of the borate is: 1′: [B(C₆F₅)₄]⁻5′: [B(C₆H₃(CF₃)₂)₄]⁻ 2′: [(C₆F₅)₂BF₂]⁻ 6′: [B (C₆H₃F₂)₄]⁻ 3′:[B(C₆H₄CF₃)₄]⁻ 7′: [C₆F₅BF₃]⁻ 4′: [B(C₆F₄OCF₃)₄]⁻; wherein the cationicentity of the borate is: [(Φ)₂I]⁺ [C₈H₁₇—O—Φ—I—Φ]⁺ [(Φ—CH₃)₂I]⁺[C₁₂H₂₅—Φ—I—Φ]⁺ [(C₈H₁₇—O—Φ)₂I]⁺ [(C₈H₁₇—O—Φ—I—Φ)]⁺ [(Φ)₃S]⁺[(Φ)₂—S—Φ—O—C₈H₁₇]⁺ [(CH₃—Φ—I —Φ—CH₃)₂]⁺ [Φ—S—Φ—S—(Φ)₂]⁺ [(C₁₂H₂₅—Φ)₂I]⁺[(CH₃—φ—I—Φ—OC₂H₅]⁺; and wherein the composition has a volumetricpolymerization and/or crosslinking shrinkage of less than 1.5% v/v. 13.The dental composition as claimed in claim 12, wherein Z is an organicsubstituent Z1 comprising at least one reactive epoxy, or dioxolanefunctional group.
 14. The dental composition as claimed claim 13,wherein the reactive functional group Z1 is:


15. The dental composition as claimed in claim 12, wherein thephotoinitiator is: [(Φ)₂I]⁺, [(C₆F₅)₄]⁻ [(C₈H₁₇)—O—Φ—I—Φ)]⁺, [B(C₆F₅)₄]⁻[C₁₂H₂₅—Φ—I—Φ]⁺, [B(C₆F₅)₄]⁻ [(C₈H₁₇—O—Φ)₂I]⁺, [B(C₆F₅)₄]⁻[(C₈H_(17l )—O—Φ—I—Φ)]) ⁺, [B(C₆F₅)₄]⁻ [(Φ)₃S]⁺, [B(C₆F₅)₄]⁻[(Φ)₂S—Φ—O—C₈H₁₇]⁺, [B(C₆H₄CF₃)₄]⁻[(C_(12 H) ₂₅—Φ)₂I]⁺, [B(C₆F₅)₄]⁻[(Φ)₃S]⁺, [B(C₅F₄OCF₃)₄]⁻ [(Φ—CH₃)₂I]⁺, [B(C₆F₅)₄]⁻ [(Φ—CH₃)₂I]⁺,[B(C₆F₄OCF₃)₄]⁻ [CH₃—Φ—I—Φ—CH(CH₃)₂]⁺, [B(C₆F₅)₄]⁻ (η⁵-cyclopentadienyl)(η⁶-toluene) Fe⁺, [B(C₆F₅)₄]⁻ (η⁵-cyclopentadienyl)(η⁶-methyl-1-naphthalene) Fe⁺, [B(C₆F₅)₄]⁻ or (η⁵-cyclopentadienyl)(η⁶-cumene) Fe⁺, [B(C₆F₅)₄]⁻.
 16. The dental composition as claimed inclaim 12, wherein the photosensitizer of formula (XXII) is3,3′-carbonylbis(7-diethylaminocoumarin) or3,3′-carbonylbis(7-methoxycoumarin).
 17. A process for the preparationof a dental prosthesis or dental restoration, comprising the step ofusing a dental composition as defined in claim 12.